This invention relates to a neck structure of a synthetic resin bottle-shaped container and, more particularly, to a cap of the bottle-shaped container, constructed to enhance the decoration of a rolled on cap of thin aluminum plate called "a pilfer-proof-cap" or tamper proof cap.
Caps which are fabricated by engaging a top-closed cylindrical cap blank of thin aluminum plate with the neck of a bottle-shaped container from above, then crimpling the body of the cap blank along the outer peripheral shape of the neck, and associating the cap with the neck, called generally "a tamper-proof-cap" have been widely employed in a large quantity in a number of fields.
This tamper-proof-cap is constructed by engaging the cap with the neck of a bottle-shaped container from above, then pressing to deform the cylindrical portion to the outer periphery of the neck formed with threads thereby press-molding spiral grooves to be engaged with the threads, bending the lower end inward to engage the lower end with the lower step of a cylindrical portion formed in a large thickness formed directly under the threads from below, and further forming a notched line of perforations between the portion to be engaged with the cylindrical portion from below and the portion formed with the spiral grooves.
Since the tamper-proof-cap is constructed as described above, the notched line of perforations must be broken so as to open a bottle-shaped container having the aforementioned neck and cap structure.
Therefore, a consumer can identify that a sealed bottle-shaped container is not illegally opened but held in a sealed state by confirming the no breakage of the notched line of perforations of the tamper-proof-cap, and can purchase the bottle-shaped container of a commodity with safety.
The tamper-proof-cap can thus perform various excellent effects, but though the conventional tamper-proof-cap of this type employs a thin aluminum plate of extremely high decorativeness, the cap does not have a construction and functions to achieve this high decorativeness.
Since the cap is molded in the final shape by press molding, even if the surface is treated to have a decoration, the surface is deteriorated by the press deformation, and this deteriorates the external appearance of the cap.
However, the tamper-proof-cap is press deformed only at the portion opposed to the threads on the neck of a bottle-shaped container and a portion opposed to the lower end of a cylindrical portion, but the other portions are not necessarily deformed at all. It is considered to provide a cylindrical portion having a relatively large width between the upper end of the neck and the lower end of the neck for engaging the cap and to surface treat the surface of the cylindrical portion to have a decorative effect.